Long Island weather: Clear and cold today, rainy Christmas possible

Saturday and at least the first half of Sunday should be just fine: clear, with a daytime high around freezing during the former and a warmer 40 degrees on the latter. Rain may arrive after midday Sunday, though, forecasters said.

While the first day of winter on Monday should be sunny, like Tuesday and Wednesday, the odds are 50/50 that Christmas Eve on Thursday and Christmas itself may see rain, the National Weather Service’s Islip office predicted.

There could even be some snow showers on Christmas, the weather service said.

And look for the snow that fell during this week's storm to stick around into next week.

"You can just expect a gradual decline in our snow depth through then," weather service meteorologist James Tomasini said by telephone.

Rain, possible snow showers, and a request

Saturday night will be chilly, with a high of just 27 degrees, but winds will be calm, the weather service said.

For Sunday, the weather service predicted, "There will be a chance of snow showers inland, and rain showers along the coast...At this time looks as though the precipitation will end by late Sunday night as the disturbances move to the northeast and north."

Temperatures are expected to be in the low to mid-40s Monday through Wednesday. The high will then shoot up to the mid-50s on Christmas Eve before dropping back down to the mid-40s on Christmas, the weather service said.

On Thursday, a low pressure system will approach, delivering "some heavy rain showers and gusty southerly winds," the weather service said.

The rising air of low pressure systems, which exert less force on the Earth’s surface, can cause vapor to condense, creating clouds and showers, scientists say. In contrast, high pressure delivers fair weather as the air dries as it falls toward the ground.

Yet take heart Christmas-celebrants: The difficulty of forecasting accurately is not one the weather service shies away from admitting.

"There is the potential for heavy rain showers ahead of a strong frontal system Thursday into Friday. It is too early to be specific with amounts at this time," the forecasters said.

In addition to the rain, the weather service said, "It is possible as colder air follows behind the front Friday, that there could be a few snow showers. Timing issues are relatively minor being this far out in time with a cold frontal passage sometime Friday morning."

A front is a "transition zone" between different systems, the weather service says.

And before the latest snowfall becomes just a memory, consider helping the weather service by sending in coastal flood or shoreline impact reports from the Wednesday night and Thursday morning high tides.

Those after-the-fact details help the weather service improve its forecasts, weather service warning coordination meteorologist Nelson Vaz explained by telephone.

The weather service monitors social media during storms, so individuals who post pictures or videos can tweet at its account @nwsnewyorkny. Reports can also be sent via email — as volunteers and officials do for snowfall totals, for example — to the weather service's Islip office at okx.spotters@noaa.gov.